Light emitting diodes (LEDs) have a broad range of uses in various applications. On one end of the spectrum, LEDs are used in keychain flashlights, while on the other end of the spectrum, LEDs are used in conjunction with digital control technology in complex computer lighting networks.
The primary colors red, green and blue (RGB) can be combined in different proportions to generate almost any color in the visible spectrum. As a consequence, it is commonly known that combining the projected light from at least two LEDs of different primary colors can produce lighting with selectable colors.
In some computer lighting networks, data signals are processed using integrated circuit (IC) controllers such as the systems described in U.S. Pat. Nos. 6,150,774 and 6,016,038 by Mueller et al., both of which are hereby incorporated by reference. Use of IC technology for data processing is not without its drawbacks, however. IC controllers do not offer much in the way of flexibility because IC technology cannot be easily updated, changed, or improved once a lighting network has been put in place without considerable expense. In fact, in order to change the functionality of a computer lighting network it is often necessary to completely replace many if not all IC controller elements.
Large computer lighting networks present several challenges. Particularly large computer lighting networks that have been installed for some period of time require maintenance. Performing maintenance on such lighting networks presents special challenges when LEDs are used in certain applications such as being used as “pixels” in a video wall when it becomes necessary to replace one or more LED pixels that have burned out or have otherwise failed. It will be appreciated by one of skill in the art that replacement of an LED module solves one problem while creating another. As LEDs age, their brightness can change. Thus, installing a new LED pixel into an area that is surrounded by older LEDs with reduced brightness results in uneven brightness of LED pixels.
Uneven pixel brightness is real problem in many large computer controlled lighting networks, such as when LEDs are used as pixels in a video wall covering a large area such as the side of a building. Even if outright pixel failure doesn't prematurely occur, the LED pixels will eventually start to produce different levels of brightness or color over time, creating a splotchy effect.
Once installed, it is not possible to periodically perform calibration of LED brightness for individual LEDs without replacing the IC controllers used to process data. It will be appreciated by one of skill in the art that replacement of IC components is both expensive and inconvenient. In a large computer lighting network, replacement of IC components may not even be feasible.
Accordingly, it would desirable to be able to control the brightness levels for individual LEDs without incurring the expense or hassle of replacing integrated circuit processors.